One type of drive assembly, which is commonly found in sailing boats with a divided lateral plane, consists of an inboard-mounted engine and, coupled drivably thereto, a drive unit which comprises a reversing gear, a drive shaft leg, which extends through an opening in the bottom of the boat, and, designed at a lower end of the drive shaft leg, a housing containing an angle gear and a propeller shaft. Until now, this type of drive assembly has been used virtually exclusively in slow-moving boats such as, for example, the abovementioned sailing boats with a divided lateral plane, where the drive shaft leg with its housing is suspended in a protected manner behind the keel of the boat and thus does not run the risk of being damaged in the event of grounding or running into an object.
It is a known fact that, with an outboard drive coupled to an inboard engine, it is possible to achieve higher overall efficiency than with an inboard engine coupled to a straight shaft in fast motor boats. Until now, however, outboard drives in fast motor boats have been of the type which is pivotably suspended in the flat of the stern of the boat and thus not of the type which has a fixed drive shaft leg which, for example, extends through the bottom of the boat. The advantage of suspending the drive in the flat of the stern is that the drive can be equipped with a safety lock which is released at a given load so that the drive can be tipped up and in this way reduce the damage that would otherwise arise in the event of, for example, grounding, and that it can be trimmed at different angles in relation to the flat of the stern so as to adapt the drive angle to the loading of the boat, the speed of the boat and the weather conditions, so that optimum propulsion can be achieved under different operating conditions. The advantages of being able to trim the drive are most apparent in smaller and medium-sized fast-moving boats, for example of sizes up to about 40 feet. The larger and heavier the boat is, the less its position in the water is affected by said factors and the smaller the need to trim the drive. At the same time, the cost of the drive increases considerably, the greater the power that is to be transmitted. For these reasons, inter alia, outboard drives are seldom used in boats of sizes over 40 feet, but in this case the engines drive straight propeller shafts via inboard-mounted reversing gears. As a result, however, the possibility of reducing the damage in the event of grounding is lost. Violent grounding of a boat with straight propeller shafts therefore has serious consequences in most cases. Shafts and bearing brackets are destroyed and, not infrequently, the engine is pulled loose from its attachments resulting in damage to the engine seatings. In the worst case, the propellers may be pushed up against the bottom of the boat and tear holes resulting in leakage which in the most serious case may lead to the boat sinking.